The present invention relates to a process for hydrolysis of naringin by means of an acid catalyst.
Naringin, which is present in grapefruit and obtained readily from grapefruit canning wastes, has the chemical formula: ##STR1##
L-rhamnose, which has sweetening properties but provides little caloric content to humans because it is not metabolized readily by the body and which may be employed as a precursor for preparation of flavoring compositions, has the chemical formula: ##STR2##
L-rhamnose is present in its free form in poison ivy and is contained in some polysaccharides of microbial origin, in some mucilages and in some plant exudates and is a constituent moiety of many glucosides, e.g., quercitrin, rutin and naringin. Prior methods to isolate and obtain useful quantities L-rhamnose involve processing steps which are not practical and economically feasible for industrial production.
Illustrative of a process for obtaining L-rhamnose from naringin is described by G. N. Pulley, et al., "Preparation of Rhamnose from Naringin", J. Amer. Chem. Soc., 61, p. 175 (1939), in which naringin is hydrolyzed by refluxing it with sulphuric acid (.about.3.7%). Glucose, L-rhamnose, naringenin and other reaction products are formed by the reaction. The reaction medium is cooled and naringenin, which is semi-solid, is separated from the cooled reaction medium. The remaining filtrate then is neutralized and heated to boiling in the presence of charcoal. The charcoal treated product is concentrated in vacuo and then is inoculated with yeast to ferment glucose. L-rhamnose is isolated from the fermented liquor by several steps of concentration in vacuo and washing.
Moreover, efforts in the art have not provided a means for treating naringin such that one might readily obtain not only L-rhamnose but also obtain naringenin-7-O-glucoside, which is useful as a starting material for the synthesis of various chemicals and pharmaceuticals, particularly capillary dilatory agents, and which has the chemical formula: ##STR3##